JP-2001-152951A describes a sensor signal processor to control an engine having an analog input circuit. In the analog input circuit, a sensor signal of a sensor detecting an operation state of the engine is inputted and converted into a digital signal, and then the digital signal and the sensor signal are digital-processed so as to output to a microcomputer. Specifically, the sensor signal is converted into the digital signal by an A/D converter at a predetermined period. The digital signal is extracted for a specified value by a digital processor. The digital signal is sent to the microcomputer by adding a crank angle information.
In this case, in a configuration for inputting an information (crank information) of the crank angle into the analog input circuit, signal wires are connected with the analog input circuit from the microcomputer. The signal wires are provided so that the crank information acquired by a hardware of the microcomputer and the crank information acquired by a software of the microcomputer are independently inputted into the analog input circuit. Further, the crank information includes a signal NE which corresponds to an angle of one tooth of a crank, a signal G2 which shows whether the crank angle is in a first half or a second half of 720 deg. CA in a four-cycle engine, and a signal of a top dead center of a cylinder. Therefore, it is necessary that six signal wires are connected with the analog input circuit from the microcomputer.
Conventionally, as described above, it is necessary to provide a plurality of signal wires between the microcomputer and the analog input circuit, which makes a size of the analog input circuit larger and leads to an increase in cost.
In a case where the crank information acquired by the software is only inputted into the analog input circuit to reduce the increase in cost, a processing load of the microcomputer may be increased. In a case where the crank information acquired by the hardware is only inputted into the analog input circuit to reduce the increase in cost, an incorrect crank information may be obtained when a rotational speed of an engine is changed at a low speed operation.